How do you calculate how long will take to download a 1GB file over 4.5 mbps speed connection

There are 1000 mbs in 1 gb and downloading at a speed of 4.5 mbps all you would need is division. Take the 1000mbs and divide it by the 4.5mbps and you'll get 222.222222222 and so forth. So approximately 222 seconds to download. Divide that by 60 seconds and you're left with 3 min. and 42 sec.